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| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2020-08-18 16:57:45 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-09-01 10:58:05 +0300 |
| commit | 1e7e47883830aae5e8246a22ca2fc6883c61acdf (patch) | |
| tree | 225d6e2fc34af21e42996c0434f871486c586a2f /arch/x86/include/asm/static_call.h | |
| parent | e6d6c071f22de29e4993784fc00cd2202b7ba149 (diff) | |
| download | linux-1e7e47883830aae5e8246a22ca2fc6883c61acdf.tar.xz | |
x86/static_call: Add inline static call implementation for x86-64
Add the inline static call implementation for x86-64. The generated code
is identical to the out-of-line case, except we move the trampoline into
it's own section.
Objtool uses the trampoline naming convention to detect all the call
sites. It then annotates those call sites in the .static_call_sites
section.
During boot (and module init), the call sites are patched to call
directly into the destination function. The temporary trampoline is
then no longer used.
[peterz: merged trampolines, put trampoline in section]
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20200818135804.864271425@infradead.org
Diffstat (limited to 'arch/x86/include/asm/static_call.h')
| -rw-r--r-- | arch/x86/include/asm/static_call.h | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h index 07aa8791cbfe..33469ae3612c 100644 --- a/arch/x86/include/asm/static_call.h +++ b/arch/x86/include/asm/static_call.h @@ -5,12 +5,23 @@ #include <asm/text-patching.h> /* + * For CONFIG_HAVE_STATIC_CALL_INLINE, this is a temporary trampoline which + * uses the current value of the key->func pointer to do an indirect jump to + * the function. This trampoline is only used during boot, before the call + * sites get patched by static_call_update(). The name of this trampoline has + * a magical aspect: objtool uses it to find static call sites so it can create + * the .static_call_sites section. + * * For CONFIG_HAVE_STATIC_CALL, this is a permanent trampoline which * does a direct jump to the function. The direct jump gets patched by * static_call_update(). + * + * Having the trampoline in a special section forces GCC to emit a JMP.d32 when + * it does tail-call optimization on the call; since you cannot compute the + * relative displacement across sections. */ #define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) \ - asm(".pushsection .text, \"ax\" \n" \ + asm(".pushsection .static_call.text, \"ax\" \n" \ ".align 4 \n" \ ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \ STATIC_CALL_TRAMP_STR(name) ": \n" \ |